Magnetoresistance effect element and magnetoresistance effect sensor

ABSTRACT

A magnetoresistance effect element includes a multilayer obtained by stacking magnetic and nonmagnetic layers to exhibit a magnetoresistance effect, and an reversal assist layer formed on the multilayer to assist reversal of a magnetic moment of the magnetic layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistance effect element anda magnetoresistance effect sensor used in a magnetic field sensor, amagnetic head, and the like and, more particularly, to amagnetoresistance effect element and a magnetoresistance effect sensorutilizing an artificial lattice film.

2. Description of the Related Art

The magnetoresistance effect is an effect in which the resistance of anobject is changed upon application of a magnetic field.Magnetoresistance effect elements that utilize this effect find avariety of applications including those for magnetic field sensors andmagnetic heads because of their high sensitivity to magnetic fields andtheir ability to produce a relatively large output. While a Permalloythin film is conventionally widely used for such magnetoresistanceeffect elements, the magnetoresistance ratio (ΔR/Rs: where ΔR is adifference in electric resistance between the zero magnetic field andthe saturated magnetic field; Rs is the electric resistance obtainedwhen the saturation field is applied) of a Permalloy film is as low asabout 2 to 3% and, therefore, does not show a satisfactory sensitivityto changes in the magnetic field.

On the other hand, as a new magnetoresistance effect element, amultilayer formed of alternately stacked magnetic and nonmagnetic layerseach having a thickness of several to several tens of Angstroms or aso-called artificial lattice film has received a great deal of attentionin recent years. Known types of the multilayers include (Fe/Cr)_(n)(Phys. Ref. Lett. vol. 61(21) (1988)2472, (Permalloy/Cu/Co/Cu)_(n) (J.Phys. Soc. Jap. vol. 59(9) (1990)3061), and (Co/Cu)_(n) (J. Mag. Mag.Mat. 94(1991)Ll; Phys. Rev. Lett. 66(1991)2152).

These multilayers exhibit a high magnetoresistance ratio as scores of %.In particular, when these multilayers are formed by using a filmformation apparatus comprising an ultra-high vacuum system, e.g., anultra-high vacuum (UHV) vapor deposition and a molecular beam epitaxy(MBE), a high magnetoresistance effect exceeding 20% can be obtained atroom temperature. Accordingly, when these multilayers are used in themagnetoresistance effect heads, a large increase in output is expected.

However, a saturation field H_(S) of the known multilayers are as strongas about 10 kOe in contrast to only several Oe for Permalloy. It followsthat, where the known multilayers are used in a magnetic sensor or amagnetic head designed to detect a weak magnetic field, the magneticsensor or head fails to exhibit a sufficient sensitivity.

More specifically, when an application as a magnetic sensor or amagnetic head is considered, it is desirable for the artificial latticefilm to exhibit a large magnetoresistance change under a weak magneticfield. To this end, the saturation field H_(S) of the artificial latticefilm is required to be diminished.

However, an artificial lattice film meeting these particularrequirements has not yet been developed.

It is proposed to use a magnetoresistance effect head utilizing themagnetoresistance effect described above to read data recorded on amagnetic recording medium (IEEE MAG-7, 150, (1971)). In recent years, asthe size reduction and capacity increase of a magnetic recording mediumhave been in progress, the relative speed of the data reading magnetichead and the magnetic recording medium during data read has beendecreased. Hence, a magnetoresistance effect head capable of obtaining alarge output even at a low relative speed is expected.

When a magnetoresistance effect head is to be put into practical use,two types of bias magnetic fields must be applied to this head. One biasmagnetic field is generally called a transverse bias to be applied in adirection perpendicular to the sense current of the magnetoresistanceeffect element. The transverse bias is a magnetic field which is applieduntil the magnitude of an external signal and that of a detection signalreach a proportional state, i.e., a so-called operating point. Anexample of a method of applying the transverse bias includes a self-biasscheme disclosed in Published Examined Japanese Patent Application Nos.53-37205 and 56-40406 and the like and a shunt-bias scheme disclosed inPublished Examined Japanese Patent Application No. 53-25646 and thelike. According to the self-bias scheme, a soft adjacent layer is formedadjacent to a magnetoresistance effect film through a thin nonmagneticfilm, and a magnetic field generated by the sense current is utilized asthe transverse bias. A method of applying the transverse bias by flowinga current through a coil disposed adjacent to a magnetoresistance effectfilm is disclosed in Published Examined Japanese Patent Application No.53-37206. A method of a hard magnetic film with a magnetization in onedirection formed adjacent to a magnetoresistance effect film in order toapply the horizontal bias is disclosed in Published Examined JapanesePatent Application No. 54-8291 and the like.

The other bias magnetic field is generally called a longitudinal bias tobe applied in a direction parallel to the sense current of themagnetoresistance effect element. The longitudinal bias suppressesBarkhausen noise which is caused since the magnetoresistance effectelement has a large number of magnetic domains. In other words, thelongitudinal bias serves to minimize the number of magnetic walls whichcause noise generation.

Various methods have been conventionally proposed to apply thelongitudinal bias. For example, U.S. Pat. No. 4,103,315 discloses that auniform longitudinal bias is generated in a magnetoresistance effectfilm by exchange-coupling an antiferromagnetic film and a ferromagneticfilm. According to JOURNAL OF APPLIED PHYSICS VOL. 52, 2472, (1981),when an FeMn alloy film is used as an antiferromagnetic film and aPermalloy (Ni₈₀ Fe₂₀) film is used as a magnetoresistance effect film, avertical bias is applied to the magnetoresistance effect film due to themagnetic exchange coupling of the alloy and Permally films. In any ofthese cases, the spin of the magnetoresistance effect film is fixed inone direction by the longitudinal bias to suppress the Barkhausen noise.

As another example of the method of applying the longitudinal bias, inaddition to the methods described above, a method of using anone-direction magnetized ferromagnetic film in the same manner as thatemployed for applying the transverse bias is proposed. According to thismethod, the longitudinal bias, the transverse bias, and an intermediatebias of the two biases can be applied by selecting the direction ofmagnetization. Magnetic Recording Laboratory, MR-37, the Institute ofElectronic and Communication Engineers of Japan introduces a method ofapplying the longitudinal bias by forming a CoP film at the end portionof a yoke type magnetoresistance effect film.

In this manner, various methods have been proposed to apply thelongitudinal bias. When, however, these methods are applied to themagnetic head for hard disk drive, the following problems arise.

Of these methods of applying the longitudinal bias, one with which themost preferable characteristics can be expected in an application to themagnetic head for hard disk drive is a method of forming an FeMn alloy(γ-FeMn alloy) film as an antiferromagnetic film on a magnetoresistanceeffect film made of a Permalloy or the like.

The longitudinal bias magnetic field is desirably of 10 to 30 Oe.

However, the FeMn alloy seriously adversely affects the reliability ofthe magnetoresistance effect element, as is reported in Nippon KinzokuGakkai (Japanese Metal Society) (543), fall 1990, since Mn is easilyoxidized. When an antiferromagnetic film is to be formed by sputtering aγ-FeMn alloy, an α-FeMn alloy phase is sometimes formed, as is pointedout in JOURNAL OF APPLIED PHYSICS VOL. 52, 2471, (1981), and it isdifficult to obtain a stable γ-FeMn alloy phase in the industrial level.

Regarding the longitudinal bias to be applied, if it is weaker than theantimagnetic field at the edge portion of the magnetoresistance effectfilm, the magnetoresistance effect film fails to have a single magneticdomain; if it is weaker than this, the sensitivity of themagnetoresistance effect film is decreased. Hence, the longitudinal biasto be applied preferably has a strength to cancel the antimagnetic fieldat the edge portion of the magnetoresistance effect film. The strengthof the antimagnetic field depends on the shape of the magnetoresistanceeffect element, i.e., the width and depth of the tracks, and the filmthickness. Hence, the level of the exchange-coupling energy must bechanged in accordance with the specifications of the magnetic head bycontrolling the shape of the magnetoresistance effect element. However,in order to control the exchange-coupling energy between the FeMn alloyas the antiferromagnetic film and the NiFe alloy as themagnetoresistance film, the thickness of the NiFe or FeMn alloy filmmust be changed, as described in the above JOURNAL OF APPLIED PHYSICSVOL. 52, 2471, (1981). When the thickness of the NiFe alloy film ischanged, the characteristics of the magnetic head itself are changed.Thus, it is not preferable to arbitrarily change the thickness of theNiFe alloy film. When the thickness of the FeMn alloy film is increased,an α-FeMn alloy phase is formed in the film, which is similarlynon-preferable. In this manner, it is actually very difficult to changethe exchange-coupling energy in accordance with the specifications ofthe magnetic head.

Furthermore, as is pointed out in JOURNAL OF APPLIED PHYSICS VOL. 53,2005, (1982), the exchange-coupling energy between the FeMn alloy andthe NiFe alloy largely depends on the temperature, and thecharacteristics of the magnetoresistance effect element may beundesirably changed by the environmental conditions and heat generationby the sense current. In order to avoid these drawbacks, IEEE TRANS.MAG-24, 2609 (1988) discloses a method of exchange-coupling a TbCo alloywith an NiFe alloy. However, since the TbCo alloy is easily oxidized,long-term reliability is not guaranteed even if the environmentalconditions where the alloy is to be used are limited.

The method of applying the longitudinal bias by the ferromagnetic bodywith a magnetization in one direction is effective if themagnetoresistance effect film is formed to be spaced apart from themagnetic recording medium, as in the yoke type magnetoresistance effecthead. However, if the magnetoresistance effect film is formed close tothe magnetic recording medium, as in the sealed type magnetoresistanceeffect head, the magnetic recording medium may undesirably bedemagnetized by the leakage magnetic field from the ferromagnetic body.When the coercive force of the ferromagnetic member is decreased toavoid demagnetization, the direction of magnetization of theferromagnetic body may undesirably be changed by the leakage magneticfield of the magnetic recording medium.

In this manner, the conventional methods of applying the longitudinalbias have various drawbacks when they are applied to a magneticrecording system in which a magnetoresistance effect film and a magneticrecording medium are adjacent to each other, as in a case wherein themagnetoresistance effect head for hard disk drive is used.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetoresistanceeffect element having a weak saturation field and capable of obtaining alow magnetoresistance ratio with a weak magnetic field.

It is another object of the present invention to provide amagnetoresistance effect element capable of obtaining a highmagnetoresistance ratio and decreasing the noise by suppressinggeneration of magnetic walls when the magnetoresistance effect elementis applied to a magnetic sensor, e.g., a magnetic head.

It is still another object of the present invention to provide a highlysensitive magnetoresistance effect sensor producing little Barkhausennoise, in which a bias magnetic field can be applied to themagnetoresistance effect film without disturbing the bias magnetic fieldby the magnetic field of a magnetic recording medium or the like.

According to an aspect of the present invention, there is provided amagnetoresistance effect element comprising: a multilayer obtained bystacking magnetic and nonmagnetic layers to exhibit a magnetoresistanceeffect; and a reversal assist layer, formed in contact with themultilayer, to assist reversal of a magnetic moment of the magneticlayer.

According to another aspect of the present invention, there is provideda magnetoresistance effect element comprising: a first multilayerobtained by stacking magnetic and nonmagnetic layers to exhibit amagnetoresistance effect; and a second multilayer obtained by stackingmagnetic and nonmagnetic layers to exhibit a saturation field largerthan that of the first multilayer, wherein the second multilayer isformed on at least an end portion of the first multilayer to apply abias magnetic field to the first multilayer.

According to still another aspect of the present invention, there isprovided a magnetoresistance effect sensor comprising: a substrate; amagnetoresistance effect layer having a magnetoresistance effect; a biasapplying layer which is obtained by stacking magnetic and nonmagneticlayers and in which two magnetic layers adjacent to each other with oneof the nonmagnetic layers interposed therebetween areantiferromagnetically coupled to apply a bias to the magnetoresistanceeffect layer; and a conductive layer formed on the magnetoresistanceeffect layer or the bias applying layer, wherein the sensor detects amagnetic field from a change in electric resistance of themagnetoresistance effect layer.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a graph showing the relationship between the thickness of thenonmagnetic layer and the magnetoresistance ratio;

FIG. 2 is a graph showing the relationship between the thickness of thenonmagnetic layer and the saturation field;

FIGS. 3 to 6 are sectional views showing magnetoresistance effectelements according to the first embodiment of the present invention;

FIG. 7 shows a film forming apparatus used in the present invention;

FIGS. 8 and 9 are sectional views showing magnetoresistance effectelements according to the second embodiment of the present invention;

FIG. 10 is a sectional view showing an arrangement of amagnetoresistance effect sensor according to the third embodiment of thepresent invention;

FIG. 11 is a sectional view showing the structure of a bias applyinglayer of the magnetoresistance effect sensor of FIG. 10;

FIG. 12 is a graph showing the relationship between the externalmagnetic fields and the magnetoresistance ratios of Example 1 togetherwith that of Comparative Example 1;

FIG. 13 is a graph showing the relationship between the thicknesses ofthe Supermalloy layers of Example 2 and the magnetoresistance ratio, andrelationship between the thickness and the saturation fields;

FIGS. 14A, 14B, and 14C are graphs respectively showing the relationshipbetween the external fields and the magnetoresistance ratios of samplesNos. 21 and 22 of Example 3 and Comparative Example 2;

FIG. 15 is a graph showing the relationship between the externalmagnetic field and the magnetoresistance ratio of sample No. 23 ofExample 4 and Comparative Example 4;

FIG. 16 is a graph showing the relationship between the externalmagnetic fields and the magnetoresistance ratios of sample No. 24 ofExample 5 and Comparative Example 5;

FIG. 17 is a graph showing the relationship between the externalmagnetic field and the magnetoresistance ratio of sample No. 25 ofExample 6 and Comparative example 6;

FIG. 18 is a graph showing the relationship between the thickness of thePermalloy layer as a reversal assist layer and the saturation fields,and relationship between the thickness and the magnetoresistance ratio;

FIG. 19 is a perspective view showing a magnetoresistance effect headusing a magnetoresistance effect element prepared in Example 6.

FIGS. 20A and 20B are views showing examples of a boundary portionbetween the magnetoresistance effect layer and the bias applying layer;

FIG. 21 is a graph showing a change in saturation field H_(S) and achange in exchange-coupling energy J when the thickness of thenonmagnetic layer is changed;

FIG. 22 is a perspective view showing a magnetoresistance effect sensorin which a magnetic anisotropy is imparted to the magnetoresistanceeffect layer;

FIG. 23 is a sectional view showing another magnetoresistance effectsensor in which a magnetic anisotropy is imparted to themagnetoresistance effect layer;

FIG. 24A is a graph showing a magnetization curve of themagnetoresistance effect sensor shown in FIG. 15 obtained by measurementin the (100)-axial direction of the MgO substrate;

FIG. 24B shows a minor loop near the origin of FIG. 24A;

FIG. 25 is a graph showing a magnetization curve of themagnetoresistance effect sensor shown in FIG. 23 obtained by measurementin the (110)-axial direction of the MgO substrate;

FIG. 26 shows the relationship between the NiFe film thickness and thebias magnetic field characteristics obtained when the numbers of stackedlayers are 60 and 15;

FIGS. 27A and 27B are views showing other arrangements of themagnetoresistance effect sensor according to the third embodiment of thepresent invention;

FIG. 28 is a sectional view showing a magnetoresistance effect sensor inwhich the magnetic field generated by the sense current is applied asthe horizontal bias;

FIGS. 29A to 29D are sectional views for explaining the steps of forminga magnetically insulating layer between artificial lattice films;

FIGS. 30A to 30D are sectional views for explaining the steps offabricating a magnetoresistance effect sensor in which the sensecurrents in two magnetoresistance effect layers are set opposite to thesignal currents;

FIGS. 31 to 33 are views showing still other arrangements of themagnetoresistance effect sensor according to the third embodiment of thepresent invention;

FIGS. 34A and 34B show a magnetoresistance effect sensor in which thehorizontal bias is applied in accordance with the soft adjacent layerscheme; and

FIGS. 35 and 36 show still other arrangements of the magnetoresistanceeffect sensor according to the third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedwith reference to the accompanying drawings.

According to the first embodiment of the present invention, there isprovided a magnetoresistance effect element comprising: a multilayerobtained by stacking magnetic and nonmagnetic layers to exhibit amagnetoresistance effect; and a reversal assist layer, formed in contactwith the multilayer, to assist reversal of a magnetic moment of themagnetic layer.

The present inventors have made extensive studies on a magnetoresistanceeffect element with which a high magnetoresistance ratio can be obtainedwith a weak magnetic field, and have found the fact that a saturationfield can be decreased, while maintaining a sufficiently highmagnetoresistance ratio, by forming, on a multilayer obtained bystacking magnetic and nonmagnetic layers to exhibit a magnetoresistanceeffect, a reversal assist layer for assisting reversal of the magneticmoment of the magnetic layer. That is, since the magnetic moment of themagnetic layer constituting the multilayer becomes to be reversed easilydue to the presence of the reversal assist layer, the magnetic moment ofthe magnetic layer can be reversed with a weak magnetic field whilemaintaining the high magnetoresistance ratio by the multilayer. Hence, ahigh sensitivity can be obtained. This embodiment is based on thesefindings of the present inventors.

The magnetic layer constituting the multilayer is formed of, e.g., atransition metal such as Fe, Co, or Ni, or alloys containing at leastone of such transition metals. More specifically, Fe_(x) Co_(1-x),Ni_(x) Fe_(1-x), Ni_(x) Co_(1-x) or Ni_(x) (Fe_(y) Co_(1-y))_(1-x)alloys are preferable. It is preferable that two magnetic layers thatare adjacent each other with one of the nonmagnetic layers interposedtherebetween are antiferromagnetically coupled to each other while nomagnetic field is substantially applied. Antiferromagnetic couplingmeans that two magnetic layers that are adjacent each other with one ofnonmagnetic layers interposed therebetween are coupled to each othersuch that their magnetic moments are in the opposite directions. Withthis coupling, the magnetoresistance ratio can be increased. When theantiferromagnetic coupling force is small, the saturation field H_(S)can be diminished, and the resultant magnetoresistance effect element issuitable as an application including a magnetic head. The thickness ofthe magnetic layer is preferably 0.1 nm to 10 nm. If the thickness ofthe magnetic layer falls outside this range, the magnetoresistance ratiotends to be decreased. A further preferable film thickness is 0.5 nm to7 nm. The film thicknesses and compositions of the respective magneticlayers need not be the same.

The material of the nonmagnetic layer is not particularly restricted asfar as it is nonmagnetic and it exhibits a good magnetoresistanceeffect. For example, a metal such as Cr, Ru, Cu, Al, Ag, or Au, or analloy containing such a metal can be used. The film thickness of thenonmagnetic layer is preferably 0.5 nm to 10 nm. If the film thicknessof the nonmagnetic layer falls outside this range, the magnetoresistanceratio is decreased. A further preferable film thickness is 0.7 nm to 7nm. The film thicknesses and compositions of the respective nonmagneticlayers need not be the same.

The thickness and the magnetoresistance ratio of the nonmagnetic layersatisfy the relation as shown in FIG. 1. Since the magnetoresistanceratio oscillates with respect to the thickness of the nonmagnetic layer,it is preferable that the thickness of the nonmagnetic layer isdetermined within the range described above to obtain a highmagnetoresistance ratio. As shown in FIG. 2, the saturation field alsooscillates with respect to the thickness of the nonmagnetic layer, andthe peak position of the saturation field overlaps the peak position ofthe magnetoresistance ratio. Accordingly, it is preferable that thethickness of the nonmagnetic layer is determined to balance themagnetoresistance ratio and the saturation field in accordance with theapplications. Note that FIGS. 1 and 2 are graphs obtained at roomtemperature by measuring a multilayer obtained by stacking 16 pairs ofmagnetic and nonmagnetic layers by using an Fe₀.1 Co₀.9 layer having athickness of 1 nm as each magnetic layer and a Cu layer having athickness of 1 nm as each nonmagnetic layer.

The multilayer is formed by stacking these magnetic and nonmagneticlayers.

The reversal assist layers have a function of assisting reversal of themagnetic moment of the magnetic layers constituting the multilayer. Inorder to exhibit this function, the reversal assist layer may be formedof a magnetic material having a softer magnetism than that of themultilayer. The reversal assist layer can exhibit above function when itis formed of a magnetic material having a softer magnetism than that ofthe magnetic layer having the hardest magnetism. To have the softmagnetism means that the direction of the magnetic moment can be easilyreversed, and the soft magnetism can be represented by, e.g., a coerciveforce (Hc). That is, the smaller the Hc, the softer the magnetism. It isassumed that when the reversal assist layer is formed of such a softmagnetic material that can be easily reversed, the magnetic moment inthe magnetic layer is easily reversed by the mutual function of thereversal assist layer and the magnetic layer. Examples of the materialconstituting the reversal assist layer are a transition metal such asFe, Co, or Ni, and an alloy containing such a transition metal, and amaterial exhibiting a soft magnetism, e.g., a conventional soft magneticmaterial such as Permally, Supermalloy, or Sendust is preferable. Thefilm thickness of the reversal assist layer is preferably about 0.5 nmto 100 nm, and more preferably 0.5 nm to 20 nm. In order to perform sucha function as a reversal assist layer, the reversal assist layer may bemade of a material having a soft magnetism, or the magnetism of thereversal assist layer may be set soft by increasing the film thickness.That is, even if the same material as that of the magnetic layer isused, the reversal assist function can be performed if the thicknessesof the reversal assist layers are larger than that of the magneticlayers. Naturally, the film thickness may be increased as compared tothat of the magnetic layer while using a material having a softmagnetism. Occasionally, a reversal assist layer preferably has a highelectric resistance. Then, a large quantity of current can be suppliedto the multilayer having the magnetoresistance effect.

The multilayer and the reversal assist layer having themagnetoresistance effect as described above are generally supported on asubstrate. In this case, the material of the substrate is notparticularly limited. Examples of the material constituting thesubstrate are MgO, Cr, GdAs, Si, Cu, Fe, Co, Ni, LiF, and CaF₂.

In this embodiment, reversal assist layers are stacked on a multilayerbasically having the above-described magnetoresistance effect to form anelement. At this time, the number of multilayers may be one or more. Amultilayer or multilayers may be formed after a reversal assist layer orlayers are formed. Furthermore, reversal assist layers may be formedbetween a plurality of multilayers, or between every two adjacentmagnetic layers.

The reversal assist layer can be disposed on an outerend portion of themultilayer and can contact to the magnetic layer of the multilayer.Also, the reversal assist layer can be interposed between the substrateand the multilayer, and can contact to the nonmagnetic layer of themultilayer.

The number of reversal assist layers may be one or more. For example, aplurality of reversal assist layers may be stacked with nonmagneticlayers interposed therebetween, and a multilayer having the abovemagnetoresistance effect may be stacked on the reversal assist layers.

At least one of the reversal assist layers can be interposed between twoof the magnetic layers, the magnetic layer and the nonmagnetic layer, ortwo of the nonmagnetic layers of the multilayer.

For example, when a state wherein m or n (m≠n) magnetic layers M eachhaving a film thickness tM and m or n nonmagnetic layers N each having afilm thickness tN are alternately stacked to form a multilayer isrepresented as (tMM/tNN)_(n), (tNN/tMM)_(n), (tMM/tNN)_(m), or(tNN/tMM)_(m), a state wherein l (l is an integer more than 1)multilayers and l reversal assist layers M' each having a film thicknessof tM' are alternately stacked is represented as [tM'M'/(tMM/tNN)_(n)]_(l), [tM'M/tNN/(tMM/tNN)_(n) ]_(l), [(tMM/tNN)_(n) /tM'M']_(l),[(tMM/tNN)_(n) /tMM/tM'M']_(l), [tM'M/(tNN/tMM)_(n) ]_(l),[tM'M/(tNN/tMM/tMM)_(n) ]_(l), [(tNN/tMM)_(n) /tM'M]_(l), or[(tNN/tMM)_(n) /tNN/tM'M]_(l), [(tNN/tMM)_(m) /tM'M/(tNN/tMM)_(n) ]_(l).Any of the cases described above, it is preferable that the reversalassist layer or layers made of the soft magnetic material and one or twomagnetic layers in the multilayer contact each other.

The practical structure of the magnetoresistance effect element of thisembodiment will be described. FIG. 3 shows an arrangement in which amultilayer 4 obtained by alternately stacking magnetic and nonmagneticlayers 2 and 3 is formed on a substrate 1, and a reversal assist layer 5is formed on the multilayer 4.

FIG. 4 shows an arrangement in which a reversal inversion assist layer 5is formed on a substrate 1, and a multilayer 4 is formed on the reversalassist layer 5.

FIG. 5 shows an arrangement having a plurality of multilayers 4, inwhich reversal assist layers 5 are present between the respectivemultilayers 4.

FIG. 6 shows an arrangement in which a plurality of inversion assistlayers 5 are stacked on a substrate 1 with nonmagnetic layers 6interposed therebetween, and a multilayer 4 is formed on the uppermostinversion assist layer 5.

A magnetoresistance effect element having an arrangement as describedabove is formed in accordance with an ordinary thin film forming method,e.g., vapor deposition, sputtering, or molecular beam epitaxy (MBE).Film formation or annealing may be performed in a magnetic field todecrease the saturation field.

FIG. 7 shows an ion beam sputtering system as an example of a filmforming system. An exhaust port 12 of a chamber 11 is connected to avacuum pump (not shown), and the pressure in the chamber 11 is measuredby a pressure gauge 13. A substrate holder 14 is placed in the chamber11, and a substrate 15 is held by the substrate holder 14. A heater 16is provided to the substrate holder 14. Cooling water 17 flows near thesubstrate holder 14 to adjust the temperature of the substrate holder 14and the substrate 15. The temperature of the substrate holder 14 ismeasured by a thermocouple 18. A shutter 19 is provided in front of thesubstrate 15. A target holder 20 is rotatably provided at a positionopposing the substrate 15, and a plurality of targets 21 are mounted onthe surface of the target holder 20. The target holder 20 is cooled bycooling water 22. An ion gun 23 is provided at a position opposing thetargets 21, and Ar gas 24 is supplied to the ion gun 23.

With this arrangement, ions from the ion gun 23 are projected toward thetargets 21. Then, the targets 21 are sputtered and the elementsconstituting the targets 21 are deposited on the substrate 15.

The second embodiment of the present invention will be described.

According to the second embodiment of the present invention, there isprovided a magnetoresistance effect element comprising a firstmultilayer obtained by stacking magnetic and nonmagnetic layers toexhibit a magnetoresistance effect, and a second multilayer obtained bystacking magnetic and nonmagnetic layers to exhibit a saturation fieldstronger than that of the first multilayer, wherein the secondmultilayer is formed on at least an end portion of the first multilayerto apply a bias magnetic field to the first multilayer.

In this embodiment, the first multilayer mainly bears themagnetoresistance effect and will be referred to as the MR portionhereinafter. The second multilayer replaces a conventional FeMn layerand will be referred to as the magnetization stabilization portionhereinafter.

Since the MR portion has a weak saturation field, it can change themagnetization state in response to a weak magnetic field from arecording medium. As a result, the MR portion can easily cause a changein resistance in accordance with the magnetic field. The magnetizationstabilization portion is formed at least at the end portion of the MRportion. Since the saturation field of the magnetization stabilizationportion is stronger than that of the MR portion, the magnetization stateof the magnetization stabilization portion cannot be easily changed byan external magnetic field. Accordingly, when a bias magnetic field isapplied to the MR portion by the magnetization stabilization portion,the magnetic layer of the magnetization stabilization portion and themagnetic layer of the MR portion are magnetically coupled so thatmagnetic walls will not be easily generated in the MR portions, therebyproviding a low-noise magnetoresistance effect head.

For example, a so-called artificial lattice film formed by stacking,e.g., a magnetic layer having a thickness of 0.5 nm to 5 nm and anonmagnetic layer having a thickness of 0.5 nm to 10 nm is used in theMR portion or in the magnetization stabilization portion. The magneticlayers of the MR portion and the magnetization stabilization portion maybe formed of Fe, Co, or Ni, or alloys containing at least one of suchelements. The nonmagnetic layers of the MR portion and the magnetizationstabilization portion may be formed of Cr, Ru, Cu, Al, or Au, or alloyscontaining at least one of such elements. As the MR portion, a(Co/Cu)_(n), (Co-Fe/Cu)_(n), (Permalloy/Cu/Permalloy)_(n), or(Permalloy/Co/Cu)_(n) multilayer can be used. As the magnetizationstabilization film, an (Fe/Cr)_(n), (Fe/Ru)_(n), or (Co/Cu)_(n)multilayer film can be used.

The value of the saturation field can be changed by changing thethickness of the nonmagnetic layers, e.g., the Cu layers, of the MRportion or the magnetization stabilization portion. Thus, a multilayerincluding nonmagnetic layers having different film thicknesses may becommonly selectively used as both the MR portion and the magnetizationstabilization portion. In this case, of the multilayer, nonmagneticlayers having a smaller film thickness are preferably used as themagnetization stabilization portion, and nonmagnetic layers having alarger film thickness are preferably used as the MR portion.Furthermore, the saturation field of multilayer can be decreased byimparting a magnetic anisotropy to the magnetic layer of multilayer.Thus, a multilayer having a magnetic layer imparted with the magneticanisotropy may be used as the MR portion, and a multilayer not impartedwith the anisotropy and having a large saturation field may be used asthe magnetization stabilization portion. It is effective if a ratioH_(S1) /H_(S2) of the saturation field H_(S1) of the MR portion to thesaturation field H_(S2) of the magnetization stabilization portionsatisfies H_(S1) /H_(S2) ≧1/5.

The magnetization stabilization portion and the MR portion aremagnetically coupled to each other so that a bias magnetic field isapplied from the magnetization stabilization portion to the MR portion.That is, it suffices if the magnetization stabilization portion and theMR portion are so coupled as to be magnetically influenced. In thiscase, it is preferable that they are magnetically coupled with anonmagnetic layer interposed therebetween because the coupling strengthis increased. The bias magnetic field to be applied to the MR portion ispreferably a vertical magnetic field. Furthermore, magnetizationstabilization portions are preferably formed only at two end portions ofthe MR portion. The magnetization stabilization portions suffice if theycan apply a strong bias magnetic field to the MR portion and need nothave a magnetoresistance effect.

In this embodiment as well, the respective multilayers are supported ona substrate. In this case, the material of each substrate is notparticularly limited, as in the first embodiment, and MgO, Cr, GdAs, Si,Cu, Fe, Co, Ni, LiF, CaF₂, or the like can be used as the material ofthe substrate.

The practical structure of the magnetoresistance effect elementaccording to the second embodiment will be described. A first multilayer41 obtained by alternately stacking magnetic and nonmagnetic layers 32and 33 is formed on a substrate 31. A second multilayer 42 obtained byalternately stacking magnetic and nonmagnetic layers 34 and 35 is formedon the first multilayer 41 to obtain the structure as shown in FIG. 8.Then, the second multilayer 42 is micropatterned to form amagnetoresistance effect element as shown in FIG. 9 in which secondmultilayers 42a are formed only on the end portions of the firstmultilayer 41. Referring to FIG. 9, arrows in the respective multilayersrepresent the direction of the spin of the magnetic layer.

In this embodiment, each multilayer can be formed easily in accordancewith RF magnetron sputtering, ion beam sputtering, vapor deposition, orthe like as well as MBE and ultra-high vacuum sputtering.

The magnetoresistance effect element obtained in this manner can be usedin a magnetoresistance effect head, a magnetic sensor, or the like.

The third embodiment of the present invention will now be described.

According to the third embodiment of the present invention, there isprovided a magnetoresistance effect sensor comprising a substrate, amagnetoresistance effect layer having a magnetoresistance effect, a biasapplying layer which is obtained by stacking magnetic and nonmagneticlayers and in which two magnetic layers that are adjacent each otherwith one nonmagnetic layer interposed therebetween areantiferromagnetically coupled to apply a bias to the magnetoresistanceeffect layer, and a conductive layer formed on the magnetoresistanceeffect layer or the bias applying layer, wherein the sensor detects amagnetic field from a change in electric resistance of themagnetoresistance effect layer.

In the magnetoresistance effect sensor according to the thirdembodiment, the bias applying layer is a multilayer film obtained bystacking the magnetic and nonmagnetic layers, the unit magnetic layer isremarkably thin, and the magnetic layers adjacent through onenonmagnetic layer are antiferromagnetically coupled. Thus, leakagemagnetic field to the outside is very small as compared to thatoccurring with a conventional hard magnetic film bias.

The magnetoresistance effect layer contacts the bias applying layerformed of the multilayer, and the magnetoresistance effect film and thebias applying layer are exchange-coupled. Hence, a predetermined biasmagnetic field can be applied to the magnetoresistance effect layer fromthe bias applying layer. At this time, the value of the bias magneticfield can be controlled by the exchange coupling force. The exchangecoupling force can be controlled over a wide range up to several hundredtimes in accordance with the thickness and type of each nonmagneticlayer of the multilayer. As a result, the predetermined bias magneticfield according to the specifications of a required magnetoresistanceeffect sensor can be easily applied.

The material of the substrate is not particularly limited, and Al₂ O₃-TiO₂ -based ceramics can be suitably used.

As the material of the magnetoresistance effect layer, a material havinga high magnetoresistance effect, e.g., an NiFe alloy such as an Ni₈₀Fe₂₀ alloy (Permalloy), an NiCo alloy, and the like can be used. Themultilayer as described above may be used as the magnetoresistanceeffect layer.

As the material of magnetic layer of the bias applying layer, transitionmetal or an alloy containing such metal, for example, Co, Fe, or a CoFealloy can be used. The thickness of the magnetic layer is preferably 0.3nm to 10 nm. If the thickness of the magnetic layer is less than 0.3 nm,antiferromagnetic coupling between adjacent magnetic layers isdecreased; if the thickness of the magnetic layer exceeds 10 nm, amagnetostatic energy from each magnetic layer is increased, and thethickness of the entire multilayer is increased.

As the material of the nonmagnetic layer of the bias applying layer, atleast one element selected from the group consisting of Cu, Ru, Cr, Rh,Re, V, W, Mo, Ta, and Nb can be used. The thickness of the nonmagneticlayer is preferably 0.5 nm to 10 nm. If the thickness of the nonmagneticlayer falls outside this range, antiferromagnetic coupling betweenadjacent magnetic layers is decreased.

Antiferromagnetic coupling means that two magnetic layers that areadjacent each other with a nonmagnetic layer interposed therebetween arecoupled to each other such that their magnetic moments are in theopposite directions. Both exchange coupling and magnetostatic couplingare acceptable.

In the bias applying layer, if Co is used as the material of themagnetic layer and if Ru, a CuNi alloy, or the like is used as thematerial of the nonmagnetic layer, the resultant magnetoresistanceeffect sensor exhibits an excellent corrosion resistance as compared tothat using an antiferromagnetic member made of an FeMn alloy or thelike.

In the bias applying layer, the strength of the bias magnetic field tobe applied to the magnetoresistance effect layer and the saturationfield H_(S) representing the stability of the bias applying layer as awhole in the magnetizing direction can be separately controlled bychanging the thickness of the nonmagnetic layer closest to themagnetoresistance effect layer and the thicknesses of other nonmagneticlayers, and by utilizing the magnetic anisotropy, e.g., crystal magneticanisotropy. For example, the strength of the bias magnetic field to themagnetoresistance effect layer can be controlled while maintaining aremarkably strong saturation field H_(S) of as high as 500 to 1,000kA/m. As a result, the characteristics of the bias applying layer can beprevented from being disturbed by the magnetic field from the magneticrecording medium.

The conductive layer is formed on the magnetoresistance effect layer orthe bias applying layer, and Cu or the like can be used as the materialof the conductive layer.

The bias applying layer can be formed by a thin-film forming technique,e.g., ultra-high vacuum sputtering, ion beam sputtering, or the like, inthe same manner as the artificial lattice films of the first and secondembodiments.

As the longitudinal bias to be applied to the magnetoresistance effectlayer, a conventionally used shunt bias, soft magnetic film bias, ortwo-layer magnetoresistance film bias can be used.

The number of magnetic layers to be alternated with the nonmagneticlayers in the bias applying layer must be two or more. The number ofmagnetic layers may be equal or not equal to the number of nonmagneticlayers. When they are not equal, e.g., when the number of magnetic layeris an even number and the number of nonmagnetic layers is an odd number,the uppermost and lowermost layers of the artificial lattice film can beset anti-parallel to each other. At this time, if the magnetic layer ofthe bias applying layer contacts the magnetoresistance effect layer,they are ferromagnetically exchange-coupled. If the nonmagnetic layer ofthe bias applying layer contacts the magnetoresistance effect layer,they are magnetostatically coupled. In either case, an effective biasmagnetic field is applied to the magnetoresistance effect layer to setthe magnetoresistance effect layer to include a single magnetic domain.

When bias applying layers are formed only on the two end portions of themagnetoresistance effect layer, the vertical bias magnetic field neednot be strictly adjusted, thus simplifying the element.

The particle structure of the magnetoresistance effect sensor of thisembodiment will be described. FIG. 10 shows an arrangement of a sensorof this embodiment. In FIG. 10, reference numeral 51 denotes asubstrate. Shunt bias layers 52 and 53, magnetoresistance layer 54, abias applying layer 55 and a conductive layer 56 are formed on thesubstrate 51, in this order. The bias applying layer 55 has anartificial lattice film structure in which magnetic and nonmagneticlayers 61 and 62 are alternately stacked, as shown in FIG. 11.

EXAMPLES

Examples of the first to third embodiments of the present invention willbe described. Note that Examples 1 to 6 concern the first embodiment,that Example concerns the second embodiment, and that Example 8 concernsthe third embodiment.

EXAMPLE 1

Using the ion beam sputtering system shown in FIG. 7 described above,magnetoresistance effect elements as shown in Table 1 were fabricated inaccordance with the following procedures.

The interior of the chamber 11 was evacuated to a vacuum degree of4×10⁻⁷ Torr, Ar gas 24 (purity:99.99%) was supplied to the ion gun 23until the partial pressure reached 1.5×10⁻⁴ Torr, and Ar was ionized andradiated to targets 21 as an ion beam having an acceleration voltage of700 V and a beam current of 30 mA. The targets 21 included three types,i.e., a target made of Co as a magnetic metal to constitute the magneticlayer of the multilayer that exhibited the magnetoresistance effect, atarget made of Cu as a nonmagnetic metal to constitute the nonmagneticlayer, and a target made of an 80 wt % Ni 20 wt % Fe alloy (to bereferred to as Permalloy hereinafter) as a magnetic metal to constitutethe reversal assist magnetic layer. The target holder 20 was switchinglyrotated every predetermined period of time. The film thickness of Cu wasset to 1 nm, the film thickness of Cu was set to 1.1 nm, the number ofrepetition times of the Co and Cu layers was set to 60, and the filmthickness of the Permalloy layer was changed in the range of 2.5 nm to50 nm. Single-crystal MgO (110) was used as the material of thesubstrate 15, and the substrate temperature was set to room temperature.In addition to sample Nos. 1 to 10, a sample of Comparative Example 1 inwhich a Permalloy layer as the reversal assist layer was not formed wasfabricated in this manner.

                  TABLE 1                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Sample No.                                                                    1        2.5 nm Permalloy/(1 nm Co/1.1 nm Cu).sub.60 /MgO                     2        5 nm Permalloy/(1 nm Co/1.1 nm Cu).sub.60 MgO                        3        10 nm Permalloy/(1 nm Co/1.1 nm Cu).sub.60 /MgO                      4        30 nm Permalloy/(1 nm Co/1.1 nm Cu).sub.60 /MgO                      5        50 nm Permalloy/(1 nm Co/1.1 nm Cu).sub.60 /MgO                      6        5 nm Permalloy/(1 nm Cu/1.1 nm Co).sub.60 /MgO                       7        5 nm Permalloy/1 nm Co/(1.1 nm Cu/                                            1.1 nm Co).sub.60 MgO                                                8        (1 nm Co/1.1 nm Cu).sub.60 /2.5 nm Permalloy/MgO                     9        (1.1 nm Cu/1 nm Co).sub.60 2.5 nm Permalloy/MgO                      10       5 nm Permalloy/1 nm Co/(1.1 nm Cu/1 nm Co).sub.60 /                           2.5 nm Permalloy/MgO                                                 Comparative                                                                            1(1.1 nm Cu/1 nm Co).sub.60 /MgO                                     Example 1                                                                     ______________________________________                                    

The magnetoresistance effects of the magnetoresistance effect elementsfabricated in the above manner with respect to the external magneticfield were measured in accordance with the ordinary four point method.

FIG. 12 shows the relationship between the external magnetic field (H)and the magnetoresistance ratio (ΔR/Rs) of Comparative Example 1 andsample No. 2. It is seen from FIG. 12 that, in Comparative Example 1wherein no reversal assist layer is formed, the magnetoresistance ratio(ΔR/Rs) is 35% and the saturation field (H_(S)) is 6 kOe, whereas insample No. 2, although the magnetoresistance ratio (ΔR/Rs) is 35%without any change, the saturation field (H_(S)) is largely decreased to1 kOe. In this manner, it was confirmed that the magnetoresistanceeffect element exhibited a better magnetoresistance effect by providinga reversal assist layer.

The same measurements as that described above were conducted for thesamples of other examples, and results similar to that of sample No. 2were obtained.

Furthermore, samples were fabricated by changing the materialsconstituting the magnetic and nonmagnetic layers of the multilayers andtheir thicknesses, and their magnetoresistance effects and saturationfields were measured. Similar effects to that of sample No. 2 wereobtained.

EXAMPLE 2

Using a 79 wt % Ni 16 wt % Fe 5 wt % Mo alloy (to be referred to as theSupermalloy hereinafter) as the soft magnetic material to constitute thereversal assist layer, using a 1-nm thick Co₀.9 Fe₀.1 alloy (to bereferred to as the Co9Fe hereinafter) as the magnetic layer of themultilayer having the magnetoresistance effect, using a 1.1-nm thick Cufilm as the nonmagnetic layer, setting the number of repetition times ofthe Co9Fe alloy layer and the Cu layer to 60, and using single-crystalMgO (110) as the material of the substrate, magnetoresistance effectelements having the film structures as shown in Table 2 were fabricatedin accordance with the same method as in Example 1. In addition tosample Nos. 11 to 19, a sample of Comparative Example 2 in which aPermalloy layer as the reversal assist layer was not formed wasfabricated in this manner.

                  TABLE 2                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Example No.                                                                   11        2.5 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                         Cu/1 nm Co9Fe).sub.60 /MgO                                          12        5 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                           Cu/1 nm Co9Fe).sub.60 /MgO                                          13        10 nm Supermalloy/1 nm Co9Fe/(1.1 m                                           Cu/1 nm Co9Fe).sub.60 /Mgo                                          14        30 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                          Cu/1 nm Co9Fe).sub.60 /MgO                                          15        50 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                          Cu/1 nm Co9Fe).sub.60 MgO                                           16        5 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                           Cu/1 nm Co9Fe).sub.60 /2 nm Supermalloy/MgO                         17        (1.1 nm Cu/1 nm Co9Fe).sub.60 /2.5 nm                                         Supermalloy/MgO                                                     18        (1.1 nm Cu/1 nm Co9Fe).sub.30 /2 nm                                           Supermalloy/(1.1 nm Cu/1 nm Fe9Fe).sub.60 /MgO                      19        5 nm Supermalloy/1 nm Co9Fe/(1.1 nm                                           Cu/1 nm Co9Fe).sub.30 /2.5 nm Supermalloy/                                    (1.1 nm Cu/1 nm Co9Fe).sub.60 /MgO                                  Comparative                                                                             2(1.1 nm Cu/1 nm Co9Fe).sub.60 MgO                                  Example 4                                                                     ______________________________________                                    

The influences of the magnetoresistance ratio (ΔR/Rs) of themagnetoresistance effect elements fabricated in this manner with respectto the external magnetic field (H) were measured.

FIG. 13 shows the relationship between the thickness of the Supermalloylayers of sample Nos. 11 to 15 and the magnetoresistance ratio, and therelationship between the thickness and the saturation field. It can beseen from FIG. 13 that the magnetoresistance ratio is 40% and thesaturation field is 4 kOe when no Supermalloy layer is provided, whereasthe magnetoresistance ratio becomes 47% and the saturation field becomes2 kOe only by providing a 2.5-nm thick Supermalloy layer. Also, when thefilm thickness is increased, although the magnetoresistance ratio isgradually decreased, the saturation field is greatly decreased. In thismanner, it was confirmed that a high magnetoresistance ratio wasobtained with a weak magnetic field by providing a reversal assist layermade of a soft magnetic material. Similar effects were obtained forother samples measured in a similar manner.

Furthermore, as the soft magnetic layer constituting the reversal assistlayer, samples using various materials, e.g., 85 at % Fe 5 at % Al 10 at% Si (Sendust), 45 at % Ni 25 at % Co 30 at % Fe (Permendur), 90 at % Co10 at % Zr, or the like were fabricated. Their magnetoresistance effectswere measured, and similar effects to that described above wereobtained.

EXAMPLE 3

Using a 5-nm thick Fe film as the soft magnetic material to serve as thereversal assist layer, using a 1-nm thick Co9Fe alloy as the magneticlayer of the multilayer having the magnetoresistance effect, using a1.1-nm thick Cu film as the nonmagnetic layer, setting the number ofrepetition times of the magnetic and nonmagnetic layers to 15, usingsingle-crystal MgO (110) as the material of the substrate, and providingan Fe buffer layer between the substrate and the multilayer,magnetoresistance effect elements having the film structures as shown inTable 3 were fabricated in accordance with the same method as inExample 1. In addition to sample Nos. 21 and 22 of Example 3, a sampleof Comparative Example 3 in which an Fe layer as the reversal assistlayer was not formed was fabricated.

                  TABLE 3                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Sample No.                                                                    21       5 nm Fe/(1 nm Co9Fe/1 nm Cu).sub.15 /5 nm Fe/MgO                     22       5 nm Fe/1 nm Cu/(1 nm Co9Fe/1 nm Cu).sub.15 /5 nm                             Fe/MgO                                                               Comparative                                                                            1 nm Cu/(1 nm Co9Fe/1 nm Cu).sub.15 /5 nm Fe/MgO                     Example 3                                                                     ______________________________________                                    

The relationship between the external magnetic fields and themagnetoresistance ratios of the magnetoresistance effect elementsfabricated in this manner was evaluated in the same manner as in Example1.

FIGS. 14A, 14B, and 14C show the influences of the magnetoresistanceratios of sample Nos. 21 and 22 and Comparative Example 3 on theexternal field. It can be seen from FIGS. 31A, 31B, and 31C that therespective saturation fields (H_(S)) are 700 Oe, 1.4 kOe, and 1.6 kOeindicating that the saturation field of Comparative Example 3 isincreased, whereas the magnetoresistance ratios are all 30% indicatingsubstantially no change. In this manner, it was confirmed that thesaturation field could be decreased while maintaining a highmagnetoresistance ratio by providing a reversal assist layer.

EXAMPLE 4

Using two 5-nm thick Ni₀.8 Fe₀.2 films, with a 1-nm thick Cu layerinterposed therebetween, as the soft magnetic layers serving as thereversal assist layers, using a 0.7-nm thick Fe₀.25 Co₀.75 alloy as themagnetic layer and a 1-nm thick Cu film as the nonmagnetic layer,respectively, of the multilayer having the magnetoresistance effect,using single-crystal MgO (110) as the material of the substrate, andproviding an Fe buffer layer between the substrate and the multilayer,magnetoresistance effect elements having the film structures as shown inTable 4 were fabricated in accordance with the same method as inExample 1. In addition to sample No. 23 of Example 4, a sample ofComparative Example 4 in which a reversal assist layer was not formedwas fabricated.

                  TABLE 4                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Sample No.                                                                             (5 nm Ni.sub.0.8 Fe.sub.0.2 /1 nm Cu/5 nm Ni.sub.0.8 Fe.sub.0.2               /(0.7 nm                                                             23       Fe.sub.0.25 Cu.sub.0.75 /1 nm Cu).sub.7).sub.2 /5 nm Fe/MgO          Comparative                                                                            (0.7 nm Fe.sub.0.25 Cu.sub.0.75 /1 nm Cu).sub.16 /5 nm Fe/MgO        Example 4                                                                     ______________________________________                                    

The influences of the magnetoresistance ratios of the magnetoresistanceeffect elements fabricated in this manner on the external magnetic fieldwas evaluated in the same manner as in Example 1.

FIG. 15 shows the relationship between the external magnetic field andthe magnetoresistance ratios of sample No. 23 of Example 4 andComparative Example 4. Referring to FIG. 15, reference symbol a denotessample No. 23; and b, Comparative Example 4. It can be seen from FIG. 32that the saturation fields (H_(S)) are respectively 3 kOe and 6.5 kOeindicating that the saturation field of Comparative Example 4 is largewhereas the both magnetoresistance ratios are 25% indicatingsubstantially no change. In this manner, it was confirmed that thesaturation field could be decreased while maintaining a highmagnetoresistance ratio by providing a reversal assist layer.

EXAMPLE 5

Using a 4-nm thick Fe film as the soft magnetic material to serve as thereversal assist layer, using a 1.5-nm thick Ni₀.4 (Fe₀.5 Co₀.5)₀.6 alloyas the magnetic layer of the multilayer having a magnetoresistanceeffect, using a 1-nm thick Cu film as the nonmagnetic layer, usingquartz as the material of the substrate, and providing a 5-nm Fe bufferlayer between the substrate ad the multilayer, magnetoresistance effectelements having the film structures as shown in Table 5 were fabricatedin accordance with the same method as in Example 1. In addition tosample No. 24 as the sample of Example 5, a sample of ComparativeExample 5 in which an Fe layer as the reversal assist layer was notformed was fabricated.

                  TABLE 5                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Sample No.                                                                             (4 nm Fe/(1.5 nm Ni.sub.0.4 (Fe.sub.0.5 Co.sub.0.5).sub.0.6 /1                nm Cu).sub.3).sub.5 /                                                24       5 nm Fe/Mgo                                                          Comparative                                                                            (1.5 nm Ni.sub.0.4 (Fe.sub.0.5 Co.sub.0.5).sub.0.6 /1 nm             Example 4                                                                              Cu).sub.16 /5 nm Fe/MgO                                              ______________________________________                                    

The relationship between the external magnetic field and themagnetoresistance ratio of the magnetoresistance effect elementsfabricated in this manner was evaluated in the same manner as in Example1.

FIG. 16 shows the relationship between the external magnetic fields andthe magnetoresistance ratios of sample No. 24 and Comparative Example 5.In FIG. 16, reference symbol a denotes sample No. 24; and b, ComparativeExample 5. It can be seen from FIG. 16 that the saturation fields(H_(S)) are respectively 0.9 kOe and 2 kOe indicating that thesaturation field of Comparative Example 5 is large, whereas therespective magnetoresistance ratios are 16% indicating substantially nochange. In this manner, it was confirmed that the saturation field couldbe decreased while maintaining a high magnetoresistance ratio byproviding a reversal assist layer.

EXAMPLE 6

Using a 2.5 nm thickness Permalloy film as the soft magnetic material toscene as the reversal assist layer, using a 1 nm thickness C0.9Fe alloyas the magnetic layer of the multilayer having the magnetoresistanceeffect, using 1 nm thick Cu film as the nonmagnetic layer, setting thenumber of repetition times of the magnetic and nonmagnetic layers to 60,using single-crystal MgO (110) as the material of the substrate,magnetoresistance effect element having the film structures as shown inTable 6 were fabricated in accordance with the same method as inExample 1. In addition to sample No. 25 as the sample of Example 6, inwhich a Permalloy layer as the reversal assist layer was not formed wasfabricated.

                  TABLE 6                                                         ______________________________________                                        Film Structure                                                                ______________________________________                                        Sample No.                                                                             2.5 nm permalloy/(1 nm Co9Fe/1 nm Cu).sub.60 /MgO                    25                                                                            Comparative                                                                            (1 nm Co9Fe/1 nm Cu).sub.60 /MgO                                     Example 4                                                                     ______________________________________                                    

The relationship between the external magnetic field and themagnetoresistance ratio of the magnetoresistance effect elementsfabricated in this manner was evaluated in the same manner as in Example1.

FIG. 17 shows the relationship between the external magnetic field andthe magnetoresistance ratio of the sample No. 25 and Comparative Example6. In FIG. 17 reference symbol a denotes sample No. 25; and b,Comparative Example 6. It can be seen from FIG. 17 that the saturationfields (H_(S)) are respectively 2.4 kOe and 3.7 kOe indicating that thesaturation field of Comparative Example 6 is large, whereas themagnetoresistance ratios are the same each other. In this manner, it wasconfirmed that the satrucation field could be decreased whilemaintaining a high magnetoresistance ratio by providing a reversalassist layer.

Next, changing the thickness of the Permalloy layer, the influence ofthe magnetoresistance ratio (ΔR/Rs) of the magnetoresistance effectelements fabricated in this manner with expect to the external magneticfield (H) were measured.

FIG. 18 shows the relationship between the thickness of the Permalloylayers and the saturation field, and the relationship between thethickness and the magnetoresistance ratio.

It can be seen from FIG. 18 that the saturation field 3.2 KOe when noPermalloy layer is provide, whereas the saturation field decreases 2 KOeby providing 2.5 nm thick Permalloy layer. ΔR/Rs value is maintained 47to 50% even if the thickness of the Permalloy layer changes. In thismanner, it was confirmed that a low saturation field was obtainedmaintaining a high magnetoresistance ratio by providing a reversalassist layer of a soft magnetic material having suitable thickness.

EXAMPLE 7

An example in which (Co₀.9 Fe₀.1 /Cu/Permalloy)n multilayer was used asthe MR portion and a (Co/Cu)_(n) multilayer was used as themagnetization stabilization portion will be described below. Filmdeposition was performed in accordance with the ion beam sputteringapparatus shown in FIG. 7.

The interior of the chamber 11 was evacuated until a vacuum degree of5×10⁻⁷ Torr, Ar was introduced until 1×10⁻⁴ Torr, and sputtering wasperformed at 500 V-30 mA. As the targets 21, an Fe₀.1 Co₀.9 alloy, aPermalloy, Co, and Cu were prepared. Quartz was used to form a substrate15. A (25 Å Fe₀.1 Co₀.9 /30 Å Cu)₂₀ multilayer 21 was formed on thesubstrate 15, and a (10 Å Co/10 Å Cu)₃₀ multilayer 22 sputtered with aCu film was formed on the multilayer 21 (see FIG. 8). The resultantstructure was patterned by micropatterning to have a structure as shownin FIG. 9. This (10 Å Co/10 Å Cu)₃₀ multilayer was used as a secondmultilayer 22a serving as the magnetization stabilization portion.

The magnetoresistance effect of only the first multilayer 21 serving asthe MR portion of the element which was patterned to have the structureas shown in FIG. 9 was measured. Although the magnetoresistance ratiowas 12% indicating no change, the saturation field was decreased to 50Oe, and substantially no hysteresis was observed. This may be becausegeneration of the magnetic walls was suppressed by the magnetizationstabilization portion 22a serving as the multilayer having a strongsaturation field, thus unidirectionally stabilizing magnetization of theMR portion 21. This means that a low-noise magnetoresistance effect headcan be provided with this method.

The magnetoresistance effects of the (25 Å F₀.1 Co₀.9 /30 Å Cu)₂₀multilayer (MR portion) and the (10 Å Co/10 Å Cu)₃₀ multilayer(magnetization stabilization portion) fabricated as a comparativeexample were measured. The magnetoresistance ratios were 12% and 2%, andthe saturation fields were 150 Oe and 9 kOe.

In this manner, although the saturation field of the MR portion wasconsiderably smaller than that of the magnetization stabilizationportion, it was still excessively large to be applied to amagnetoresistance effect head. Also, the hysteresis was observed. Thismay be because magnetization of the MR film was partially deviated fromone direction to increase the saturation field, causing the hysteresisin the MR curve.

The magnetoresistance effect element obtained in this manner can be usedin a magnetoresistance head to derive a signal magnetic flux as a signalcurrent from a magnetic recording medium 81 by a lead wire 82, as shownin FIG. 19.

EXAMPLE 8

In this example, various magnetoresistance sensor of the thirdembodiment are described. In the sensor shown in FIG. 10 describedabove, shunt bias layers 52 and 53 for applying the horizontal bias aresequentially formed on the substrate 51. The shunt bias layer 52 is abias current layer made of Ti or the like, and the shunt bias layer 53is a high-resistant layer made of TiN, TiO₂, or the like. Amagnetoresistance effect layer 54 made of an NiFe alloy or the like isformed on the shunt bias layer 53. A bias applying layer 55 for applyingthe vertical bias magnetic field to the magnetoresistance effect layer54 is formed on the magnetoresistance effect layer 54. A conductivelayer 56 for supplying a current to the magnetoresistance effect layer54 is partially formed on a region of the bias applying layer 55.

The bias applying layer 55 is the multilayer film structure in whichmagnetic and nonmagnetic layers 61 and 62 are alternately stacked andwhich includes at least two magnetic layers 61, as shown in abovedescribed FIG. 11. Each magnetic layer 61 is made of Co, Fe, a CoFealloy, or the like, and each nonmagnetic layer 62 is made of Cu, Cr, orthe like. The magnetic and nonmagnetic layers 61 and 62 are alternatelystacked in this manner, and the magnetic layers 61 that are adjacentthrough one nonmagnetic layer 62 are antiferromagnetically coupled. As aresult, the vertical bias magnetic field can be applied from a magneticlayer 61 of the bias applying layer 55 which is closest to themagnetoresistance effect layer 54 to the magnetoresistance effect layer54 formed under the bias applying layer 55 as the multilayer.

In the interface of the magnetoresistance effect layer 54 and the biasapplying layer 55, the magnetic layer 61 of the bias applying layer 55contacts the magnetoresistance effect layer 54, as shown in FIG. 20A, orthe nonmagnetic layer 62 of the bias applying layer 55 contacts themagnetoresistance effect layer 54, as shown in FIG. 20B. When thecrystal structures of the magnetoresistance effect layer 54 and themagnetic layers 61 are different (e.g., when an NiFe film is used as themagnetoresistance effect layer 54 and Fe films are used as the magneticlayers 61), if the nonmagnetic layer 62 and the magnetoresistance effectlayer 54 contact each other, magnetic coupling between the magneticlayers 61 and the magnetoresistance effect layer 54 is weakened.Therefore, the structure of FIG. 20A in which the magnetoresistanceeffect layer 54 and the magnetic layer 61 contact each other ispreferable.

The saturation field H_(S) and the exchange-coupling energy J can becontrolled by changing the thicknesses of the nonmagnetic layers 62 ofthe bias applying layer 55. For example, FIG. 13 shows changes insaturation field H_(S) and exchange-coupling energy J obtained bychanging the thicknesses of nonmagnetic layers 62 in a bias applyinglayer 55 having structure of using Co as the material of the magneticlayers 61 and Cu as the material of the nonmagnetic layers 62, whereinthe numbers of magnetic and nonmagnetic layers 61 and 62 having a unitfilm thickness of 1.8 nm are respectively set to eight. Theexchange-coupling energy J can be obtained from the saturation fieldH_(S) of the bias applying layer 55 measured from the magnetizationcurve in accordance with the following equation (1):

    H.sub.S =4·J/(d·Ms)                      (1)

where Ms is the saturation magnetization of each magnetic layer 61 and dis the thickness of each magnetic layer.

As is apparent from FIG. 21, the exchange-coupling energy(exchange-coupling force), i.e., the bias magnetic field to be appliedto the magnetoresistance effect layer 54 can be controlled by adjustingthe thickness of each nonmagnetic layer 62. Furthermore, theexchange-coupling force can be adjusted by changing the material of eachnonmagnetic layer 62. Table 1 shows examples of the exchange-couplingforce. Table 1 shows the relationship between the types of thenonmagnetic layers 62 of the bias applying layer 55 having the structureof a thickness of 1.8 nm and the exchange-coupling energy J. Note thatthe thickness of each nonmagnetic layer 62 is set to a value with whicha maximum J can be obtained by using the corresponding material.

                  TABLE 7                                                         ______________________________________                                        Type of         Exchange-Coupling                                             Nonmagnetic Layer                                                                             Energy (μJ/m.sup.2)                                        ______________________________________                                        Cu              300                                                           Cr              200                                                           V               140                                                           Mo               52                                                           W                15                                                           Ta               9                                                            Nb               30                                                           Re              120                                                           Ru              700                                                           Rh              1500                                                          ______________________________________                                    

As can be seen from Table 1, the value of J can be controlled with awide range of 9 to 1,500 μJ/m² by changing the material of thenonmagnetic layer.

It is preferable that the saturation field H_(S) is increased as much aspossible in order to prevent degradation of the bias applying layer 55caused by the magnetic field applied by a magnetic recording medium orthe like. However, as can be seen from equation (1), since thesaturation field H_(S) is proportional to the exchange-coupling energyJ, when H_(S) is increased, J is also increased accordingly to sometimesreach an excessively high value. This problem can be avoided if thethickness or the material of the nonmagnetic layer 62 of the biasapplying layer 55 which is closest to the magnetoresistance effect layer54 is adjusted to optimize the value of the bias magnetic field to beapplied to the magnetoresistance effect layer 54 and independently ifthe thickness or the material of other nonmagnetic layers is adjusted toincrease H_(S).

The bias applying layer 55 having the structure described above canapply a bias to the magnetoresistance effect layer 54 in a predetermineddirection in accordance with a method to be described below.

Assume that a magnetic anisotropy having the x direction of FIG. 10 asthe easy axis of magnetization is applied to the magnetic layers of thebias applying layer. When an external magnetic field stronger than theantiferromagnetic coupling force between the magnetic layers of the biasapplying layer is applied in the x direction, magnetization of themagnetic layers 61 that are antiferromagnetically coupled stably existsin the x direction even after the external magnetic field is removed. Asa result, the longitudinal bias can be applied to the magnetoresistanceeffect layer 54 in the x direction by the antiferromagnetic couplingforce between the magnetic layers 61 and the magnetoresistance effectlayer 54.

Note that the magnetic anisotropy can be applied in accordance with,e.g., the following methods.

According to the first method, films using CoFe alloy films as themagnetic layers 61, the magnetic layers 61 are formed under the magneticfield, so as to apply a uniaxial magnetic anisotropy having thedirection in which the magnetic field is applied as the easy axis ofmagnetization. The film formation temperature is preferably equal to orhigher than a temperature where antiferromagnetic coupling in theartificial lattice film disappears.

According to the second method, after the artificial lattice film isformed, the resultant structure is annealed under a magnetic field of apredetermined direction regardless of whether an NiFe alloy film as themagnetoresistance effect film is formed, so as to apply the uniaxialmagnetic anisotropy having the direction of the magnetic field duringannealing as the easy axis of magnetization. The annealing temperatureis equal to or higher than a temperature where the antiferromagneticcoupling of the artificial lattice film disappears. The magnetic fieldis preferably similarly applied even during cooling.

According to the third method, if a nonmagnetic layer region 57 isformed at least at one location on the central portion of a biasapplying layer 55 along the tracking width, a magnetic anisotropy havingthe longitudinal direction of the bias applying layer 55 as the easyaxis of magnetization can be applied, as shown in FIG. 22. In order toprovide the nonmagnetic layer region 57, shunt bias layers 52 and 53,and a magnetoresistance effect layer 54 are sequentially formed on asubstrate 51, and the bias applying layer 55 is formed on themagnetoresistance effect layer 54 by ultra-high vacuum sputtering.Subsequently, a resist is coated on the bias applying layer 55 to form aresist layer, and the resultant structure is patterned to leave the endportions of the resist layers in the longitudinal direction as themasks. The exposed bias applying layer 55, i.e., the central portionalong the tracking width in the longitudinal direction is etched by ionmilling.

The fourth method utilizes a crystal magnetic anisotropy. In anartificial lattice film using a Co-based magnetic film having an hcpphase, a strong magnetic anisotropy of several 100 kA/m, having the filmsurface direction of the artificial lattice film which is along the(100) direction of the MgO film as the easy axis of magnetization, canbe applied to the artificial lattice film by using a single-crystal MgOfilm having the (100) plane as the vertical direction of the filmsurface and forming the artificial lattice film on the MgO film.

The practical example of the fourth method will be described below indetail. For example, artificial lattice films obtained by alternatelystacking 1-nm thick Co₉ Fe films at sixty times and 1.1-nm thick Cufilms are formed on the (100) plane of a single-crystal MgO substrate,and a 1-nm thick Co₉ Fe film is formed on the uppermost artificiallattice film, as shown in FIG. 23. Subsequently, a 10-nm thick NiFe(Permalloy) film is formed on the resultant structure in accordance withion beam sputtering.

FIGS. 24A, 24B, and 25 are graphs of the magnetization of this samplemeasured by a vibration type magnetometer, in which FIGS. 24A and 24Bare graphs obtained by measuring the magnetization in the (100)-axisdirection of the MgO substrate, and FIG. 17 is a graph obtained bymeasuring the magnetization in the (110)-axis direction of the same. InFIG. 24A, the magnetization curve of the NiFe film is shown near theorigin. FIG. 24B shows the minor loop near the origin. It is seen fromFIG. 24B that a bias magnetic field of about 20 kA/m is applied to theNiFe film.

In FIG. 25, the magnetization continuously changes with respect to theapplied magnetic field corresponding to the signal magnetic field, andno hysteresis is observed in the magnetization curve. Hence, it is seenthat Barkhausen noise which accompanies when the magnetic walls aremoved is suppressed. From these respects, it is confirmed that in thissystem the (100)-axis direction of the MgO substrate is the easy axis ofmagnetization and the (110)-axis direction is the difficult axis ofmagnetization. The saturation magnetic field along the difficult axis ofmagnetization is about 1×10³ kA/m (point A in FIG. 17).

In this system, a bias magnetic field having the (100)-axis direction ofthe MgO substrate as the easy axis of magnetization was observed even ifthe thickness of the NiFe film and the number of artificial latticefilms were changed. FIG. 26 is a graph showing the relationship betweenthe NiFe film thickness and the characteristics of the bias magneticfield obtained when the numbers of multilayers are 60 and 15. It wasconfirmed from FIG. 26 that the substantially same bias magnetic fieldcould be obtained even by setting the number of artificial lattice filmsto 15. It was also confirmed that the bias magnetic field was diminishedas the thickness of the NiFe film was increased.

Therefore, according to the magnetoresistance effect sensor of thisexample, a stable longitudinal bias can be applied to themagnetoresistance effect layer 54, and Barkhausen noise caused by theinstability of the magnetization behavior can be sufficientlysuppressed. Since the vertical bias can be controlled by changing thethickness of the nonmagnetic layers or the types of the material, avertical bias of a level appropriate to the specifications of themagnetoresistance effect sensor can be applied, thereby preventing thelongitudinal bias from adversely affecting the sensor sensitivity.Therefore, a magnetic head capable of reproducing a signal having a highS/N ratio can be fabricated by using the magnetoresistance effect sensorof this embodiment.

FIG. 27A shows a magnetoresistance effect sensor in which bias applyinglayers 101 as the artificial lattice films are formed only on theregions at the two end portions of an magnetoresistance effect layer,and conductive layers 103 are formed on the bias applying layers 101. Inthis structure, since the longitudinal bias magnetic field of the biasapplying layers 101 does not easily influence a signal magnetic fieldsensitive portion 102, the longitudinal magnetic field need not bestrictly adjusted, which is preferable. Regarding the conductive layers,they need not be formed on the bias applying layers, but conductivelayers 104 may be formed on the inner sides of the bias applying layers101, as shown in FIG. 27B.

In the magnetoresistance effect sensor of this embodiment, in place ofthe conventional magnetic insulating layer, two magnetoresistance effectlayers may be formed on the substrate with a bias applying layer as theartificial lattice film intervened between them, as shown in FIG. 28,and the magnetic field generated by the sense current can be used as thetransverse bias. The magnetoresistance effect sensor of this type isformed by forming a magnetoresistance effect layer 111 on a substrate 51by sputtering or vacuum deposition, forming a bias applying layer 55 asthe artificial lattice film on the magnetoresistance effect layer 111 byultra-high vacuum sputtering, forming a magnetoresistance effect layer112 on the bias applying layer 55 in the same manner as themagnetoresistance effect layer 111, and forming a conductive layer 56 asa lead wire. At this time, if the conductive layer 56 is formed bymicropatterning in accordance with ion milling, the magnetoresistanceeffect layer 112 can be damaged. Therefore, it is preferable that theconductive layer 56 is formed by a lift-off method.

In the above structure, artificial lattice films may be formed only atregions on the two end portions of the magnetoresistance effect layer,and a magnetically insulating layer may be formed between the twoartificial lattice films. In this case, a magnetoresistance effect layer111 and a bias applying layer 121 as the artificial lattice film aresequentially stacked on a substrate 51, a resist is coated on the biasapplying layer 121 to form a resist layer 122, and the resultantstructure is patterned to leave the two end portions of the resist layer122 as the masks, as shown in FIG. 29A. Subsequently, the exposedportion of the bias applying layer 121, i.e., the bias applying layer121 excluding its two end portions is etched by ion milling, as shown inFIG. 29B. Subsequently, a magnetically insulating layer 123 is formed onthe region between the remaining bias applying layers 121 by sputteringor vapor deposition to have the same thickness as that of the biasapplying layers 121, and the resist layer 122 is removed, as shown inFIG. 29C. Note that Ti'Ta or the like is used as the material of themagnetically insulating layer 123. Then, another magnetoresistanceeffect layer 124 is formed to cover the resultant bias applying layers121 as the artificial lattice films and the magnetically insulatinglayer 123, as shown in FIG. 29D.

The magnetoresistance effect sensor of third embodiment can be appliedto a magnetic head having a high sensitivity with respect to in-phasesignals if an electrically insulating layer is formed between twoartificial lattice films and if two magnetoresistance effect layers areformed such that the sense currents flowing therein are opposite to eachother with respect to a signal magnetic field.

A magnetoresistance effect layer 131 and a bias applying layer 132 asthe artificial lattice film are sequentially formed on a substrate 51,as shown in FIG. 30A. Subsequently, an electrically insulating layer 133is formed on the bias applying layer 132 by a lift-off method, andanother bias applying layer 134 as the artificial lattice film and amagnetoresistance effect layer 135 are sequentially formed, as shown inFIG. 30B.

Note that SiO₂ or the like can be used as the material of theelectrically insulating layer 133. At this time, the magnetoresistanceeffect layers 131 and 135 are formed by sputtering or vapor deposition,and the bias applying layers 132 and 134 as the artificial lattice filmsare formed by ultra-high vacuum sputtering. Then, only one side of theresultant structure is etched by ion milling down to a mid point of thebias applying layer 132 (it suffices if this point is below the upperend portion of the electrically insulating layer 133 and above the lowerend portion of the magnetoresistance effect layer 131), as shown in FIG.30C. Subsequently, a conductive layer 136 is formed as the lead wire bypatterning, as shown in FIG. 30D.

In this structure, since the directions of sense currents I in themagnetoresistance effect layers 131 and 135 can be set opposite to eachother with respect to the signal magnetic field, as indicated by areference symbol I in FIG. 30D, and since the magnetoresistance effectlayers 131 and 135 are connected in series, the sensitivity of themagnetic head is improved.

The order of the magnetoresistance effect layer 131 and the biasapplying layer 132, and the order of the magnetoresistance effect layer135 and the bias applying layer 134 may be reversed so that themagnetoresistance effect layers 131 and 135 are formed inside the biasapplying layers 132 an 134. A bias applying layer 134 is not sometimescorrectly formed on an end portion of an electrically insulating layer143. This problem can be solved by providing a tapered portion on theend portion of the electrically insulating layer 143 by the lift-offmethod during formation of the electrically insulating layer 143, asshown in FIG. 31.

The basic structure of the magnetoresistance effect sensor according tothe third embodiment is shown in FIG. 28. However, the basic structureis not limited to this. For example, a bias applying layer 151 as theartificial lattice film, a magnetoresistance effect layer 152, amagnetically insulating layer 153, a magnetoresistance effect layer 154,and a bias applying layer 155 as the artificial lattice film can besequentially formed on a substrate 51, as shown in FIG. 32. With thisstructure, the distance between the magnetoresistance effect layers 152and 154 can be further decreased. Then, both the magnetoresistanceeffect layers 152 and 154 apply the bias magnetic fields to each otherto enhance the effect of applying the longitudinal bias.

The effect of the present invention can be obtained even ifmagnetoresistance effect layers 161 and bias applying layers 162 as theartificial lattice films are alternately stacked, as shown in FIG. 33.

In the magnetoresistance effect sensor according to this embodiment, thehorizontal bias can be applied to a magnetoresistance effect layer inthe direction of a soft adjacent layer. In this case, a soft magneticfilm 171 is formed on a substrate 51 by sputtering, a bias applyinglayer 172 as the artificial lattice film is formed on the soft magneticfilm 171 by ultra-high vacuum sputtering, and a magnetoresistance effectlayer 173 is formed on the bias applying layer 172 by sputtering orvacuum deposition, as shown in FIG. 34A. Subsequently, a conductivelayer 174 is formed as a lead wire at a desired position of themagnetoresistance effect layer 173, as shown in FIG. 34B. At this time,the conductive layer 174 is preferably formed by the lift-off method, asdescribed above.

With this structure, magnetization of the magnetoresistance effect layer173 and that of the soft magnetic film 171 can be stabilized by theirantiferromagnetic coupling with the bias applying layer 172. Then,Barkhausen noise of the magnetoresistance effect layer 173 and that ofthe soft magnetic film 171 can be suppressed.

Even if a bias applying layer 181 as the artificial lattice film, amagnetoresistance effect layer 182, a magnetically insulating layer 183,a soft magnetic film 184, and a bias applying layer 185 as theartificial lattice film are sequentially formed, as shown in FIG. 35, oreven if a magnetoresistance effect layer 191 and a soft magnetic film192 are respectively alternated with bias applying layers 193 and 194 asthe artificial lattice films, as shown in FIG. 36, based on thestructure of FIGS. 26A and 26B, the effect of this example.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices, shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A magnetoresistance effect element comprising:amultilayer obtained by stacking magnetic and nonmagnetic layers toexhibit a magnetoresistance effect; and a reversal assist layers, formedin contact with said multilayer, to assist reversal of a magnetic momentof said magnetic layer.
 2. An element according to claim 1, wherein saidreversal assist layer has a softer magnetism than that of saidmultilayer.
 3. An element according to claim 1, wherein said reversalassist layer has a film thickness larger than that of said magneticlayers of said multilayer.
 4. An element according to claim 1, whereinsaid magnetic layers of said multilayer contain Fe, Co, Ni, or an alloycontaining Fe, Co, or Ni.
 5. An element according to claim 1, whereinsaid nonmagnetic layer of said multilayers contain Cr, Ru, Cu, Al, Ag,Au, or an alloy containing Cr, Ru, Cu, Al, Ag, or Au.
 6. An elementaccording to claim 1, wherein said magnetic layers of said multilayerhave a film thickness of 0.1 nm to 10 nm.
 7. An element according toclaim 1, wherein said nonmagnetic layers of said multilayer have a filmthickness of 0.5 nm to 10 nm.
 8. An element according to claim 1,wherein said reversal assist layer is disposed on an outerend portion ofsaid multilayer and contacts to said magnetic layer of said multilayer.9. An element according to claim 1, wherein said reversal assist layeris interposed between a substrate and said multilayer, and contacts tosaid nonmagnetic layer of said multilayer.
 10. An element according toclaim 1, further comprising another reversal assist layer and/or anothermultilayer.
 11. An element according to claim 1, wherein at least one ofsaid reversal assist layers is interposed between two of said magneticlayers, said magnetic layer and said nonmagnetic layer, or two of saidnonmagnetic layers of said multilayer.
 12. A magnetoresistance effectelement comprising:a first multilayer obtained by stacking magnetic andnonmagnetic layers to exhibit a magnetoresistance effect; and a secondmultilayer obtained by stacking magnetic and nonmagnetic layers toexhibit a saturation field larger than that of said first multilayer,wherein said second multilayer is formed on at least an end portion ofsaid first multilayer to apply a bias magnetic field to said firstmultilayer.
 13. An element according to claim 12, wherein each secondmultilayer applies a longitudinal magnetic field to said firstmultilayer.
 14. An element according to claim 12, wherein each of saidmagnetic layers of said first and second multilayers has a filmthickness of 0.5 nm to 5 nm.
 15. An element according to claim 12,wherein each of said nonmagnetic layer of said first multilayer and saidnonmagnetic layer of said second multilayer has a film thickness of 0.5nm to 5 nm.
 16. An element according to claim 12, wherein said magneticlayer of said first and second multilayers contains Fe, Co, Ni, or analloy containing Fe, Co, or Ni.
 17. An element according to claim 12,wherein said nonmagnetic layer of said first multilayer has a filmthickness larger than that of said nonmagnetic layer of said secondmultilayer.
 18. An element according to claim 12, wherein said magneticlayer of said first multilayer has a magnetic anisotropy.
 19. An elementaccording to claim 12, wherein a ratio of the saturation field of saidfirst multilayer to that of said second multilayer is not more than 1/5.20. A magnetoresistance effect sensor comprising:a substrate; amagnetoresistance effect layer having a magnetoresistance effect; a biasapplying layer which is obtained by stacking magnetic and nonmagneticlayers and in which two magnetic layers adjacent to each other with oneof said nonmagnetic layers interposed therebetween areantiferromagnetically coupled to apply a bias to said magnetoresistanceeffect layer; and a conductive layer formed on said magnetoresistanceeffect layer or said bias applying layer, wherein said sensor detects amagnetic field from a change in electric resistance of saidmagnetoresistance effect layer.
 21. A sensor according to claim 20,wherein said bias applying layer applies a longitudinal bias to saidmagnetoresistance effect layer.